These studies focus on a longitudinal analysis of behavioral changes in affective illness, interrelating these observations with physiological and biological variables; emphasis is on circadian (24-hour) and longer rhythms. Results to date indicate that some regularly cycling bipolar patients show circadian desynchronization in temperature and motor activity, so that the normal rhythm is no longer "locked in" to the environmental 24-hour day-night cycle, but tends to drift in and out of phase. Alterations in this cycle can be manipulated by such procedures as day-night reversal and artificial 21-hour days. A new ambulatory non-telemetric physiological monitor has been developed and tested in inpatients and outpatients. The relationship between biological rhythms and melatonin levels can now be explored thanks to the development of a highly sensitive assay based on mass spectrometry. An immunoassay for melatonin has also been developed. BIBLIOGRAPHIC REFERENCES: Carmen, J.S., Post, R.M., Buswell, R. and Goodwin, F.K.: Negative Effects of Melatonin on Depression. Am. J. Psychiat. 131: 1181-1186, 1976. Wehr, T. and Goodwin, F.K.: Catecholamines and Depression. In Burrow, G. (Ed.): Handbook on Depression. Amsterdam, Exerpta Medica, 1977, pp. 329-348.